The present invention relates generally to the field of magnetic tape data access, and more particularly to shortening the average reposition time to the beginning of existing files in a magnetic tape.
Magnetic tape (“tape”) data storage systems are widely used to store digital data. Tape data storage systems provide increased data storage space and longevity, for reduced costs. Modern magnetic tapes are commonly packaged in tape cartridges or cassettes. A tape appliance or a tape drive is a device that performs writing or reading of digital data from the tape.
Digital data may be written on tapes of different lengths and widths. One of the standards that defines tape properties is a LINEAR TAPE OPEN® (LTO®) standard (Linear Tape Open and LTO and all LTO based trademarks and logos are trademarks or registered trademarks of Hewlett Packard Enterprise, IBM and Quantum and/or their affiliates). The LTO standard defines a raw data capacity, tape partitioning, and speed of reading of uncompressed data. For example, LTO-7 is capable of writing six terabytes of data to a 3150 ft (960 meter) tape with an average speed of 300 MB/Sec.
Tape partitioning is a creation of one or more regions (data bands) on a magnetic tape so that an operating system may manage the data in each region of the tape separately. One of the partitioning standards that was adopted by the LTO is a Linear Tape File System (LTFS). The LTFS standard formats a tape in a special way that allows to access all recorded files metadata first and therefore see the files and directories on the tape directly after mounting of the tape cartridge. In addition, due to LTFS standard being adopted by all operating systems, the files can be viewed by the operating system without any additional software and can be accessed and used as if it is a hard disk drive (HDD) or a removable flash drive file system, such as, for example, allowing the user to manage and store files in folders (directories), copy, rename and delete files, use drag and drop and copy and paste functionality without waiting while the tape appliance is reading all the data recorded on the tape.
The LTFS format defines at least two partitions on a tape that comprise a data band. One partition, known as an Index Partition (IP), is used to store the metadata of all the files and folders (henceforth “file”, “files”) recorded on a tape. The other partition is Data Partition (DP), where all the content of the files are stored including files body and files metadata. In LTFS standard, file content is appended to the end of the tape (free space) and deleted files do not′ typically, free up space on the tape.